Low profile board to board connector

Abstract: A low profile connector (20) includes a receptacle (22) and a plug (70), each having a housing (24,72) with respective arrays of contacts (44,92) secured therein, the contacts (44,92) being of thin metal set on edge in the housings (24,72) and including edge contact surfaces (50,98) projecting from the housings (24,72) in a common plane for soldering to the circuits. Each receptacle contact (44) has a C-shaped configuration including a base (48) an intermediate tortion (60) and an arm (62), the arm (62) defining a contact surface (68) adapted to mate with a corresponding plug contact surface (110), the arm (62) extending transversely of the axis in a first direction. Each plug contact (92) has an L-shaped configuration including a Ease (94) and a post (104) extending from the base (94) parallel to the axis, a side surface (110) of the post (104) defining a mating surface for a corresponding one of the receptacle contacts (44). Upon mating of the receptacle (22) and plug (70) the side surface of the post (104) of the plug contact (92) engages the arm (62) of the receptacle contact (44) in sliding engagement, deflecting the arm (62)transversely of the axis in a second direction, the post (104) co-extending past the arm (62) and in spring biased engagement therewith resulting in a low profile connector (20).

Description: This invention relates to electrical connectors and, more particularly, to board to board electrical connectors for interconnecting circuits between parallel circuit boards. U.S. Patent No. 5,199,884 discloses a blind matable miniature connector for interconnecting circuits between parallel circuit boards. The connector in this patent includes contacts placed on close center lines such as on the order 0.5 mm (0.020 inches) for high density inteconnection. Spring design of the contacts, and the housings require a minimum height of about 5 mm (0.20 inches), which means that the boards to be connected can be no closer than 5 mm (0.20 inches) apart. GB-A-1 467 381 discloses an electrical connector assembly wherein posts of a first connector are received between a pair of laterally deflectable arms of a contact in a second connector. With the increased miniaturization of electronic equipment, such as small portable computers and the like, it is desirable to have connectors that will allow circuit boards to be placed at lower stack heights on the order of 3.0 mm and 4.0 mm (0.118 inches to 0.157 inches). It is further desirable that the low profile connector contacts also provide for high density interconnections. The present invention consists in an electrical connector assembly comprising first and second connectors having respective first and second housings and respective first and second electrical contacts secured in at least one row in the associated housing, the first and second contacts include respective first and second contact sections electrically engageable along a mating interface of the first and second connectors, each said first contact section being joined to an axially extending intermediate section proximate an inner wall of the first housing being laterally deflectable upon mating, and each said second contact section being a post portion including a contact surface and extending axially along a cavity of the second housing and engageable with said first contact section, the connector assembly being characterized int hat the first contact section is a single transverse arm extending outwardly from the intermediate section towards an outer wall of the first housing and including a contact surface, whereby upon mating of the first and second connectors the contact surfaces of the first contacts and second contacts slidably engage each other deflecting the arms in a lateral direction parallel to said outer wall of the first housing, with the post portions extending along and past the arms in spring-biased engagement therewith and being spaced inwardly from said outer wall. The invention enables the provision of a low profile board to board connector assembly including a plug and receptacle, each having respective housings and arrays of contacts of thin metal set on sedge in the housing on center lines complimentary to the center lines of the circuits on the printed circuit boards.It may permit the interconnection of circuits on the surfaces of parallel circuit boards having extremely close kneader lines between the circuits. Furthermore, it enables the provision of a low profile connector assembly which permits mating of the contacts even when the contacts of each matable pair are slightly misaligned with respect to each other, thereby permitting multiple arrays of rigidly mounted contacts in multiple connectors to be mated simultaneously thus defining an arrangement that compensates for the tolerances. In a preferred embodiment, the contacts include edge contact surfaces projecting from the housings in a common plane for soldering to the board circuits. The receptacle housing includes a floor, opposed side walls, and opposed end walls, together defining an interior cavity configured to receive the plug housing inserted therein. The housing floor has a plurality of contact receiving slots extending therethrough, each slot having a receptacle contact disposed therein. The receptacle contacts have a body with a C-shaped configuration and include a base, an intermediate portion and an arm, the base and arm extending essentially parallel to one another from the intermediate portion. The outward edge of the base defines the edge contact surface for engagement with a respective circuit on a circuit board and the intermediate portion and arm define a spring, the arm including a contact surface adapted to mate with a corresponding plug contact upon mating the receptacle and plug. The receptacle contact is disposed in the slot of the housing floor such that the board contact surface thereof is spaced outwardly from the outer major surface of the floor and the intermediate portion and arm extend into the interior cavity of the receptacle housing, the arm extending transversely of the axis of mating in a first direction. The arm is adapted to be deflected transversely of the axis of mating in a second direction by the corresponding plug contact when the receptacle and plug are mated. Preferably, the plug housing includes a floor having a plurality of cavity walls extending laterally across the interior surface of the floor and a plurality of contact receiving apertures extending through the floor. Each plug contact has an L-shaped configuration including a base and a transversely directed post extending from an interior edge of the base. The outer edge of the base defines an edge contact surface for engagement with a respective circuit of a circuit board and the post defines a mating surface for a corresponding one of the receptacle contacts. The plug contact is disposed in the plug housing such that the base portion extends along the outer surface of the floor and the post portion extends through the aperture into a contact receiving cavity adjacent a respective cavity wall. Upon mating the receptacle and plug, the post of the plug contact engages the contact surface of the spring arm of the receptacle contact in a sliding engagement, deflecting the spring arm in a direction transverse to the axis of mating. The post extends past the spring arm and is in spring bias engagement therewith resulting in a low profile connector thus minimizing board to board spacing. To prevent solder from being wicked into a connector housing, each contact includes a body having opposed side surfaces and first and second portions, the first portion defines a base having a contact surface extending along an outer edge thereof for electrical connection to a circuit of a circuit board. The second portion is securable within a housing and includes a contact section for mating with a complementary contact of a mating connector. At east one side surface of the base includes at least one interruption extending at east between the edge contact surface thereof and the second body portion. Upon securing the contact within the connector housing and upon mounting the housing to a circuit board with the edge contact surface in electrical engagement with the circuit on the board, and soldering the contact surfaces top the circuit, the interruption prevents solder form being wicked into the connector housing. One or more interruptions can be located on the side body surfaces. In the preferred embodiment the receptacle and plug contacts further included a plurality of grooves on at least one side thereof to prevent solder from being wicked up into the mating area of the associated connector housing when the connector is soldered to the circuit board. Adjustment of the stacking height between parallel boards may be achieved by means of an embodiment of the plug contact in which the width of the base of the L-shaped member is selected to provide a desired stacking height. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: FIGURE 1 is a perspective view of the connector assembly of the present invention, considerably enlarged, with the receptacle and plug exploded from each other. FIGURE 2 is a perspective view of the mating side of the plug housing. FIGURE 3 is an enlarged fragmentary view of the connector assembly of Figure 1 having the receptacle and plug contacts exploded from the respective housings. FIGURE 4 is a cross-sectional view of the assembly showing the plug and receptacle mounted to respective circuit boards prior to mating of the receptacle and plug. FIGURE 5 is an end view taken along lines 5-5 of Figure 4. FIGURE 6 is a cross-sectional view similar to that of Figure 4 showing the receptacle and plug mated. FIGURE 7 is a view taken along lines 7-7 of Figure 6. FIGURE 8 is a view similar to Figure 4 illustrating a receptacle and plug having a higher stack height than the one shown in Figures 4 - 7. FIGURE 9 is a view similar to Figure 8 showing the mated connector assembly. FIGURE 10 is a perspective view of one side of the receptacle and plug contacts used in the embodiment shown in Figures 1 - 7. FIGURE 11 is a sectional view taken along the line 11-11 of Figure 10. FIGURE 12 is a view similar to that of Figure 10 showing the other side of the receptacle and plug contacts. FIGURE 13 is a sectional view taken along line 13-13 of Figure 12. FIGURE 14 is a perspective view of one side of the further embodiment of the plug contact made in accordance with the invention as shown in the embodiment of Figures 8 and 9. FIGURE 15 is a view similar to that of Figure 14 showing the other side of the plug contact. FIGURE 16 is a fragmentary enlarged view of a receptacle contact soldered to a circuit pad on a circuit board. Referring now to Figures 1, 2, 3 and 4 connector assembly 20 includes a receptacle 22 having a plurality of receptacle contacts 44 disposed therein and a plug 70 having a plurality of contacts 92 disposed therein. Receptacle 22 includes a housing 24 having a floor 26 having major inner and outer surfaces 28,30 respectively. Floor 26 further includes a plurality of contact receiving slots 32 extending therethrough between the inner and outer major surfaces 28,30. Receptacle housing 24 also includes opposed side walls 34 and opposed end walls 38, the floor 26, side walls 34 and end walls 38 together defining a cavity 42 configured to receive a portion of the plug 70 therein upon mating the receptacle 22 and plug 70. End walls 38 include apertures 40 for receiving guide pins 78 of the plug housing 72 when the receptacle 22 and plug 70 are mated. Plug 70, as shown in Figures 1 through 4, includes a plug housing 72 having a floor 74 and opposed major surfaces 76 and 80 and a plurality of contact receiving apertures 84 extending through the floor 74. The inner surface 76 of floor 74 includes posts 78, which extend forwardly therefrom for engagement with corresponding apertures 40 in the receptacle housing 24 when the plug 70 is mated to receptacle 22. The outer surface 80 of floor 74 includes posts 82 for mounting plug 70 onto a circuit board 116 as can best be seen in Figures 4 through 6. The major inner surface 76 of floor 74 further includes a center wall 86 extending longitudinally therealong. A plurality of side walls 88 extend essentially perpendicular to the center wall 86 and between the respective apertures 84 and define internal open ended cavities 90 for receiving the mating portions of the respective receptacle and plug contacts 44,92 as more fully described below. Receptacle and plug housings 24,72 respectively are preferably made from a high temperature resistant material such as a liquid crystal polymer or the like. The material selected must be able to withstand temperatures of about 250° C that are typically achieved during a soldering process, such as infrared reflow soldering or other methods as known in the art. Receptacle ccntacts 44, as best seen in Figures 10 and 12, have C-shaped bodies 46 having opposed major surfaces 45 and 47. Body 46 includes a base 48, intermediate portion 60 and an arm 62. Base 48 has an outer contact surface 50 for engaging corresponding circuit pads 114 on circuit board 112, as shown in Figures 4 through 7, and 16. Base 48 includes a plurality of dimples or protrusions 52,53 extending outwardly from major surface 45, which aid in positioning receptacle contact 44 within the corresponding slot 32. In the preferred embodiment the receptacle contact 44 is made from metal stock material having a thickness of approximately 0.15 mm (0.006 inches). The metal selected preferably has a high yield strength in the range of 730 000 - 860 000 KN/m 2 (105-125 thousand p.s.i.) to assure that sufficient normal force is achieved in the mated assembly. The protrusions 52,53 aid in the absorbing the clearance within the slot 32 so that the other major surface 47 of the contact 44 is held flat against a wall within the slot 32. The position of protrusion 53, in particular, also influences the spring characteristics of spring arm 62 and determines the amount of stress transmitted to base 48. Base 48 further includes a retention means 54 which engages the surface of receptacle housing 24 when contact 44 is disposed within the slot 32. Also seen in Figure 4, when contact 44 is disposed within its respective slot 32, arm 62 and a portion of the intermediate portion 60 extend into the receptacle cavity 42. The base 48 of contact 44 further includes a short leg portion 56 having a groove 55 therein for receiving the side wall 34 therein. As shown in Figures 4, 10, 12 and 16 the base 48 further includes two grooves 58 on each side thereof that act to prevent the solder 59 from being wicked into the receptacle cavity, as shown in Figure 16. To ensure a good solder joint with the circuit pad 114 on board 112, the outer edge 50 of contact 44 has an indentation 51 that allows a fillet of solder to spread beneath the thin edge of the contact 44 as seen in Figure 16. The intermediate portion 60 includes an inner tapered edge 61. This tapering evenly distributes stresses along the length of portion 60 and arm 62, thus optimizing the spring characteristics of receptacle contact 44. The arm 62 is shorter than the base 48 and includes a radiused portion 66 at the leading end 64 thereof as shown in Figure 11. The radiused surface 66 provides a ramp and a contact surface 68 for engaging a corresponding contact surface 110 of the plug contact 92 when the receptacle 22 and plug 70 are mated, as is more fully described below. Referring now to Figures 4 and 5, the receptacle 22 is assembled by inserting C-shaped contact members 44 into the respective slots 32 of floor 26 from the outer surface 30 thereof such that the arm 62 extends into the cavity 42. As can be seen in Figure 4, the lower portion of base 48 extends from the outer surface 30 of housing 24 with the groove 55 capturing the respective housing side wall 34, and the retention means 54 engages an inner wall surface. The protrusions 52,53, as can best be seen in Figure 5, hold contact 44 against one of the walls of the slot 32. The solder wicking prevention grooves 58 lie approximate the outer surface 30 of floor 26. Figure 4 also shows the receptacle 22 having its terminals 44 and outer edge contact surface 50 positioned on corresponding circuit pads 114 of circuit board 112. Contact 44 is shown soldered to the pad in Figure 16, which also illustrates the function of grooves 58. As shown in Figures 10, 12 and 13, plug contacts 92 have an L-shaped configuration including a base 94 having an inner and outer surface 93,95 respectively and a transversely directed post 104 extending from an interior end thereof. The base 94 further includes a thinner area 96 which defines a thin outer edge contact surface 98 for engagement with a respective circuit 118 on a circuit board 116 as shown in Figures 4 through 7. Contact 92 is preferably made from metal stock such as phosphor bronze or the like having a thickness of approximately 0.32 mm (0.0126 inches), which preferably has reduced thickness of approximately 0.23 mm at 96 to provide the contact edge surface 98. The plug contact 92 further includes solder wicking prevention grooves 102 on one side thereof. Post 104 includes a retention area 106 for holding the contact 92 within the housing floor 74 and has a radiused and tapered section 108 at the leading end thereof leading to the contact surface 110, as seen more clearly in Figures 10, 12 and 13. The L-shaped-plug contact 92 is assembled into the plug housing 72 by inserting the post 104 into respective apertures 84 from the outer surface 80 of floor 74 such that the base 94 of the contact lies against the outer surface 80 of housing 72 and the straight side of post 104 extends adjacent one of the side walls 88 and into cavities 90, as can be seen in Figures 4 and 5. The respective contacts 92 are secured in the plug housing by means of the retention feature 106 and essentially in an interference fit. Upon mating the receptacle 22 and the plug 70, the lead-in surface 108 of post 104 of the plug contact 92 engages the corresponding contact surface 68 of the spring arm 62 of the receptacle contact 44 in sliding engagement therewith. As post 104 slides toward the floor of the receptacle housing 24, the surface 108 deflects the spring arm 62 in a direction transversely to the axis of mating. As the post 104 deflects the spring arm 62, the intermediate body portion 60 of the receptacle contact 44 twists thereby providing sufficient normal force between the two contact members. The amount of normal force can be controlled by adjusting the position of slot 32 with respect to apertures 84 thereby determining the amount of deflection of spring arm 62. When the receptacle 22 and plug 70 are fully mated, the post 104 extends past the spring arm 62 and is in spring bias engagement therewith. The resulting assembly 20 has a low profile thus minimizing the board to board spacing as can be seen in Figures 6 and 7. The configuration of the contacts 44, 92 and housings 22, 72 and the high deflection force of the contacts 44 provide a low profile connector assembly that will permit mating of the contacts 44, 92 even when the contacts 44,92 of each matable pair are slightly misaligned with respect to each other, thereby permitting multiple arrays of rigidly mounted contacts 44, 92 in multiple connectors 10 to be mated simultaneously, thus defining an arrangement that compensates for tolerances. As can be seen in Figures 10 and 12, the protrusions 52,53 are on only one side of the contact 44. Thus, when two rows of receptacle contacts 44 are inserted into housing 22, as shown in Figures 1 and 3, all the contacts 44 in the first row are urged in a common first direction in their respective slots 32 and all the contacts 44 in the second row are urged in a common second direction, opposed to the first direction. The shape of plug base 94 throws the plug contact 92 to one side of its respective aperture 84 as shown in Figures 1, 3 and 7. Thus the plug contacts 92 in the first row are thrown in a common direction opposite to that of the receptacle contacts 44 thereby enabling the corresponding contact surfaces 66, 110 to engage each other. In the same manner, the plug contacts 92 in the second row are thrown in a common direction opposite to that of the receptacle contacts 44 thereby enabling the corresponding contact surfaces 66, 110 to engage each other in the second row. By positioning the contacts 44,92 in the two rows so that the contacts 44 therein are deflected in opposing directions, torque generated in one row by the twisting of the receptacle contacts 44 during mating is cancelled out by the torque generated in the opposite direction by the contacts 44 in the other row. Figures 8, 9, 14 and 15 illustrate the present invention using another embodiment 192 of the plug contact in which the contact base 194 is wider thereby providing a greater stack height between the parallel circuit boards when the connector 120 is assembled. The base 194 of the L-shaped base of contact 192 includes the thinned area 196 and the corresponding grooves 202 to prevent solder wicking in the same manner as previously described. To reduce the capacitance of the contact 192, the base portion 194 may further include an aperture 197 as can be seen in the above Figures. Figure 8 illustrates connector assembly 120 prior to mating and Figures 9 illustrates the assembly 120 after mating.

Claims: An electrical connector assembly (20,120) comprising first and second connectors (22,70) having respective first and second housings (24,72) and respective first (44) and second (92,192) electrical contacts secured in at least one row in the associated housing, the first and second contacts including respective first and second contact sections (62,104) electrically engageable along a mating interface of the connectors, each said first contact section being joined to an intermediate section (60) extending axially of the mating direction of the connectors and being laterally deflectable upon mating, and each said second contact section being a post portion including a contact surface and extending axially of a cavity (90) of the second housing and being engageable with said first contact section, the connector assembly being characterized in that the first contact section is a single transverse arm (62) extending outwardly from the intermediate section (60) towards an outer wall (34) of the first housing (24)and including a contact surface (66), whereby upon mating of the first and second connectors (22,70) the contact surfaces (66,110,210) of the first contacts (44) and second contacts (92,192) slidably engage each other deflecting the arms (62) in a lateral direction parallel to said outer wall of the first housing (24), with the post portions (104,204) extending along and past the arms (62) in spring-biased engagement therewith and being spaced inwardly from said outer wall (34). The connector assembly of claim 1, wherein the first and second housings (24,72) include two rows of respective first (44) and second (92, 192) contacts secured in the associated housing (24,72), all of the contacts in the first row being disposed in a common first direction and all the contacts in the second row being disposed in a common second direction opposite to said direction. The connector assembly of claim 1 or 2, wherein each of the contacts (44, 92,192) includes a base (44, 94,194) having a contact surface (50,98,198) extending along an outer edge thereof for electrical connection to a circuit (114,118) of a circuit board (112,116), and a portion securable within the associated housing and wherein at least one of the opposite side surfaces of the base (44,94,194) has at least an inwardly directed interruption (58,102,202) extending across the base between the edge contact surface (50,98,198) and said portion in substantially parallel relationship to said edge contact surface, whereby upon mating the associated housing (24,72) to a circuit board (112,116) with the edge contact surface (50,98,198) in electrical engagement with a circuit (14,118) on the board (112,116), and soldering the contact surface to the circuit, the interruption (58,102,202) prevents solder from being wicked into the associated housing. The connector assembly of claim 3, wherein both opposite side surfaces of the base (44,94,194) have at least one inwardly directed interruption extending across the base between the edge contact surface and said portion in substantially parallel relationship to said edge contact surface. The connector assembly of claim 3 or 4, wherein the or each interruption is a groove (58,102,202). The connector assembly of claim 5, including two of the grooves (58,102,202) in the or each side surface.

Inventors: ENGLERT MICHAEL WAYNE, SUMMERS DONALD JAMES, ENGLERT, MICHAEL WAYNE, SUMMERS, DONALD JAMES
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1994
Main classification: H01R23
IPC codes: H01R4, H01R12, H01R13